Then the German, Diesel, invented the internal-combustion engine for heavy oil. The mazut, subjected to high pressure in a cylinder, produces an explosive mixture which, without sparking-plug or magneto, drives the pistons in the manner of a petrol engine. The installation is rather heavy, but no boiler is required, and it takes up much less space than a steam engine of the same power. A vessel fitted with a Diesel engine can sail for fifty-seven days without re-fuelling, while with a steam engine it could only sail for a fortnight. A ship fitted with a Diesel engine and having a speed of 20 knots could sail from France to Suez, India, Australia, New Zealand, and return by Cape Horn without re-fuelling. But, better than any words, the following little table, made out for two boats of the same power, will give an idea of the great advantages of the Diesel engine:-- --------------------------+--------------+--------------- | Diesel. | Steam. --------------------------+--------------+--------------- H.P. | 21,000 | 21,000 Weight of engine and | | accessories | 1,000 tons | 3,400 tons Space required | 5,300 cu. m. | 10,000 cu. m. Daily consumption | 100 tons | 360 tons | (heavy oil) | (coal) Consumption for a voyage | | of 15 days | 1,500 tons | 5,400 tons Bunker space for a voyage | | of 15 days | 1,700 cu. m. | 7,000 cu. m. Total space required for | | engine and fuel | 7,000 cu. m. | 17,000 cu. m. --------------------------+--------------+--------------- At first oil was used on fishing boats, then on small coasters. To-day the biggest British cargo boats, of the type of the _Zeelandia_ or _Sutlandia_, are fitted with Diesel engines. All German submarines had them during the War. In 1917 Herr Ballin,[2] the great friend of William II and the head of the _Hamburg-Amerika_ line, just before his suicide decided on the construction of a fleet of enormous ships fitted with internal-combustion engines. Scandinavia, Holland, Italy, all now use the Diesel engine. France alone remains behind in this respect. It has even been used on railways, a little-known fact. Diesel locomotives with four cylinders, built by Sulzer Brothers of Winterthur, have recently been run on the line from Berlin to Mannsfeld. "The development of our metallurgy," wrote Admiral Degouy in April 1920, "will soon give us the assurance that we also shall be able to manufacture large-bore cylinders and pistons of flawless casting, like those made in Augsburg, Nuremberg, Stockholm, and Christiania, which will support for long periods without change (and consequently without leakage) the temperature of 1,000° C. which is developed by the combustion of mazut in these engines."